A process for the manufacture of methyl alcohol is described in U.S. Pat. No. 4,990,696. The patent discloses a process involving three reaction steps operated in conjunction with each other. Beginning with the first step, perchloroethylene is oxychlorinated with hydrogen chloride and oxygen to obtain hexachloroethane. In the second step methane is chlorinated with hexachloroethane to produce methyl chloride, hydrogen chloride and regenerated perchloroethylene. The methyl chloride from the second step is isolated and hydrolyzed with water in the third step to give methyl alcohol and hydrogen chloride. The reactions are operated in a balanced mode by recycling perchloroethylene from the second step to the first step, and by recycling hydrogen chloride produced in each of the second and third steps to the first step.
A number of difficulties, however, are encountered with existing technology. Perhaps the greatest shortcoming is the unfavorable equilibrium in the hydrolysis reaction of methyl chloride with water to produce methyl alcohol. At ambient temperatures the reverse reaction, namely, the formation of methyl chloride from methyl alcohol and hydrogen chloride, is greatly favored. Elevated temperatures are required to shift the equilibrium, but even then only partial conversions are possible. Thus, an excess of water or steam is favored, and unreacted methyl chloride must be recycled to the hydrolysis reaction.
An additional problem identified with existing technology is the control of the temperature in the first step, namely, the oxychlorination reaction. This reaction is exothermic, and therefore heat must be removed to maintain the temperature at the desired setting. When a solid catalyst is used in this reaction, the possibility of hot spots developing on the catalyst particles ia potential problem.
Finally, the required investment in equipment must be considered. Since the existing technology involves the use of highly corrosive chemicals, especially aqueous hydrogen chloride streams, materials of construction can be a problem. Any reduction in the number of reaction steps and in the necessary unit operations, e.g., distillation, has the potential for substantial cost savings.
It is therefore an object of the present invention to provide a process that overcomes the disadvantages of existing technology for producing methyl alcohol.
A further object is to be able to produce high yields of product at minimum investment and operating costs.
These and other objects, features and advantages of the invention will be apparent from the accompanying drawing and the following description.